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Mark Cornforth, center, of the defending champion Boston Danglers, cuts between two players from Team Snuuz, of Switzerland, during the World Pond Hockey Championships in Plaster Rock, New Brunswick, Canada on February 17, 2006. Photographer: Brian Atkinson/Bloomberg News

Hockey was born more than 150 years ago in Canada, where the defining image of childhood is kids playing hockey on a frozen pond. Those kids serve an important purpose to the NHL: From the ponds come the next generation of hockey players and fans.

But as the average temperature across the globe has risen, the outdoor skating season in Canada and the northern U.S. has begun to shrink, as temperatures cold enough to keep the ice safely frozen becoming rarer and rarer.

David Phillips, a senior climatologist at Environment Canada, says the message from the data is loud and clear.

"It's not as cold and white as it used to be," he said. "If you look across the country, the one season that has shown truly dramatic changes in the last 65 years are winters."

The NHL is aware of the threat posed by climate change, and players have tried to raise awareness. In 2006, the Boston Bruins' Andrew Ference spearheaded a carbon-neutral movement with the David Suzuki Foundation, getting more than 500 players to buy carbon offsets for all the travel they do during the season.

Across the whole of Canada, the average winter (December through February) temperature has risen about 5 degrees, said Phillips. The increase has been most severe in Northern British Columbia, the Yukon and Northwest Territories, where the temperatures have jumped more than 9 degrees — making a frozen pond much rarer.

The rise in temperature has shortened the outdoor hockey season by as much as 15 days, according to a study released last year by Nikolay Damyanov at McGill University's Department of Atmospheric and Oceanic Sciences.

"Here in Canada we're quite strong in natural resources," said Jean-Patrick Toussaint, head of science projects at the Suzuki Foundation, who noted that Canada was the first country to withdraw from the Kyoto Protocol. "Not only water, but we've also got the tar sands, and this has become a top priority for our current government, to make sure that there's continuous economic growth."

The problem does cross the border. Outdoor hockey is popular in America, too, as evidenced by the the NHL's Winter Classic, an annual outdoor showcase. Five of the top six-rated regular season games since 1975 have been Winter Classics.

Last year, though, even the Winter Classic was threatened. The NHL had to delay the game between the Rangers and Flyers at Philadelphia's Citizens Bank Park until later in the day to ensure temperatures were low enough to keep the ice frozen

"Last year was one of the worst winters we've ever had for outdoor hockey," Haberman said. "If we'd tried to have the tournament last week, we would have had to cancel because it rained — it was 40 degrees.

"When I arrived in the Twin Cities (24 years ago), I was playing a minimum of 10 to 12 weeks outside. Today, we're lucky if we get eight."

Not only does the shortened outdoor hockey season deny aspiring NHLers countless hours of practice time, it also stunts their development because they grow accustomed to the perfectly groomed ice of indoor rinks, and so are less adept at handling bad hops.

"It's on these outdoor rinks where kids can just play and experiment, develop their skills without even realizing it," said Joe Pelletier of Greatest Hockey Legends. "Minor hockey is so structured nowadays that kids are essentially taught the game. But out on their own on the frozen ponds, kids actually learned the game. And the game was better off for it."

Ultimately, framing global warming as a hockey problem may be what forces Canada to confront the issue. If Canadians realize that climate change is slowly corroding not only the quality of hockey and the amount of hockey they can play in their backyard, they might force the government to act.

"The threat from climate change... Canadians are not worried about skinny polar bears," said Phillips, the climatologist at Environment Canada. "It's about, 'Gee -- will we have a white Christmas and will we be hockey players?' When it comes right down to it, it would probably drive us to action if people understood it in that way."